‹ All simulationsBiology · AS Level 9700 · 1 Cell structureSeven simulations covering Topic 1: the microscope and magnification (1.1), the organelles of eukaryotic cells (1.2), and the structure of prokaryotes and viruses (1.3). Rotate the 3D cells with drag, zoom with the wheel or pinch, and click any organelle to see what it does.
A typical animal cell as seen with an electron microscope, rebuilt in three dimensions. Click an organelle in the scene or pick it from the list. Switch to Test yourself and the sim names a function: click the organelle that does it.
Everything the animal cell has, plus three things it does not: a cellulose cell wall, chloroplasts and a large permanent vacuole. Click a chloroplast to see the grana and stroma inside.
No nucleus, no membrane-bound organelles, and about a tenth of the size of a eukaryotic cell. Click the parts, then compare the two cell types in the table.
| prokaryote | eukaryote | |
|---|---|---|
| size | 1 to 5 µm | 10 to 100 µm |
| DNA | circular, free in cytoplasm, no histones | linear, in a nucleus, wound on histones |
| ribosomes | 70S (smaller) | 80S (larger) |
| membrane-bound organelles | none | many |
| cell wall | peptidoglycan (murein) | cellulose in plants, none in animals |
Choose an objective lens and see the field of view change. Calibrate the eyepiece graticule against the stage micrometer, then click two points on a cell to measure it in graticule divisions and convert to micrometres.
An electron micrograph comes with a scale bar, not a magnification. Measure the scale bar to find the magnification, then measure the cell image to find its actual size. Drag the ruler handles; the working updates as you go.
Each step along the ladder is ten times smaller. Hover or click an object to see its size, and see which instrument can resolve it: the eye stops at about 0.1 mm, the light microscope at 200 nm, the electron microscope at about 0.5 nm.
| unit | metres | next unit |
|---|---|---|
| 1 mm | 10⁻³ m | = 1000 µm |
| 1 µm | 10⁻⁶ m | = 1000 nm |
| 1 nm | 10⁻⁹ m |
Not cells: no cytoplasm, no organelles, no metabolism of their own. A virus is genetic material inside a protein capsid, sometimes wrapped in a membrane envelope stolen from the last host cell. Compare three designs.